1. Field of the Invention
This invention relates to an improved flooring system. More particularly, the present invention relates to a flooring system that utilizes a composite underlayment.
2. Description of the Background Art
Flooring systems generally include a structural subfloor, which can be a concrete slab or wooden foundation. An underlayment is then installed over the subfloor to provide a smooth surface for the application of a floor covering. It is known in the art to use gypsum-based building materials as a flooring underlayment. Gypsum-based building materials are generally constructed by depositing a layer of cementitious gypsum slurry between two opposing paper liners. Gypsum slurry is the semi-hydrous form of calcium sulfate and has many physical characteristics that make it suitable for use as a building component. For example, gypsum boards generally have a smooth external surface, a consistent thickness, and allow for the application a covering, such as tiles or wood flooring. Gypsum-based buildings materials are desirable because they provide a degree of fire resistance and sound abatement.
An example of a gypsum-based floor underlayment is disclosed in U.S. Pat. No. 7,651,564 to Francis and assigned to Georgia-Pacific Gypsum, LLC. The Francis patent illustrates a high strength floor underlayment comprising a dry mixture of beta type gypsum, fly ash, a water reducing aid, and a conventional set retarder.
U.S. Pub. No. 20060264548 to Liu discloses a surface enhancing coating for gypsum-containing floor underlayments. The coating prepares an underlayment to receive an adhesive and includes a water-soluble latex primer, a defoamer, and a dual-function surface enhancing agent. The surface enhancing agent includes a set accelerator that also functions to cross link the adhesive and harden the surface of the underlayment.
Additionally, U.S. Pat. No. 6,673,177 to Buckwalter and assigned to Armstrong World Industries, Inc. discloses a preglued underlayment assembly. The assembly comprises a substantially rigid underlayment having an adhesive layer disposed on the upper surface. A release layer is disposed over the adhesive. Another pressure sensitive layer and another release layer are optionally provided on the lower surface of the underlayment. Furthermore, one or more performance enhancing layers, such as a foam layer or solid layer, can be disposed between the underlayment and the adhesive layer.
Although the above referenced flooring constructions achieve their own individual objectives, there exists a need in the art for a flooring underlayment with improved physical properties. More specifically, there exists a need in the art for an underlayment that can provide enhanced flexibility, water repellency, fire resistance, friction, shear resistance, and load carrying capacities. There is also a need in the art for an underlayment that provides these physical properties without unduly increasing weight or cost. The present invention is aimed at achieving these and other objectives.